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151.
Isotopes of uranium in the sea-water sediments collected from two different areas (El Hamraween harbour and Ras El Behar) on the Egyptian coast of the red sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of 238U, 235U, 234U were calculated. The activities observed indicated enhanced radioactivity levels in sea-water sediments of El Hamraween harbour area due to the activities of phosphate shipment operation. Secular equilibrium between 234U and 238U was found in the analyzed samples. The average activity ratio of 235U/238U was close to the value 0.046 for uranium in nature. 相似文献
152.
Pollution by heavy metals has become one of the most important problems in marine coastal areas as a consequence of anthropogenic inputs. Among metal contaminants, zinc, being considered not very toxic, is sometimes released into the sea in appreciable quantities and its concentration is loosely regulated.In this work we analyzed the effects of a high zinc concentration on the sea urchin Paracentrotus lividus immune system. In particular, after 24 h of zinc treatment, we evaluated coelomocytes morphology and composition as well as the zinc influence on some humoral parameters such as hemolysis, lysozyme-like activity and antibacterial activity on Vibrio alginolyticus. Our results evidenced that the presence of zinc affected both cellular and acellular components of the sea urchin immune system. The P. lividus coelomocytes changed in morphology and number; moreover, the amebocytes changed from a petaloid to a filipodial-like shape and the red spherula cells increased in number. Among the considered humoral effectors lysozyme-like activity and antibacterial activity on V. alginolyticus decreased in short-term to zinc treatment. The modifications in the sea urchin immunological competence might give an early indication of disease susceptibility thus suggesting to consider the examined defence mechanisms as potential biological indicators of metal pollution. 相似文献
153.
《Journal of environmental science and health. Part. B》2012,47(12):942-947
AbstractThe effect of fenhexamid, mepanipyrim and cyazofamid fungicides on in vitro bioavailability of antioxidant activity and phenolic compounds of Tempranillo and Graciano red wine was studied by simulating the digestive process by dialysis in semipermeable membranes. Determination of antioxidant activity was through reaction with the DPPH ? radical and the measurement of phenolic compounds was made with liquid chromatography with diode detector (HPLC-DAD). Fenhexamid, mepanipyrim and cyazofamid reduce the total polyphenol content in both wines. During dialysis there was a large loss of total polyphenols (80–90%) and of antioxidant activity (> 90%). The bioavailability of the phenolic compounds is lower than that for non-treated wines and the highest dialization percentages were found for stilbenes > 50%. While for the remaining phenolic fraction the order is the following hydroxycinnamic derivatives?>?anthocyanins?>?flavonols. 相似文献
154.
采用青霉菌菌体作为吸附剂对染料活性艳红X-3B进行吸附研究,考察了染料的初始质量浓度、pH值和温度对菌体吸附能力的影响,并探讨了吸附动力学和热力学特性.结果表明,经硝酸处理后的菌体吸附能力明显增强,在pH值为3时,吸附量达到最大. 吸附过程可用准二级动力学方程来表达,平衡时吸附量的计算值和实验值吻合很好,相关系数可达0.999 8. 硝酸处理的菌体对活性艳红的吸附等温线可用Langmuir方程表达.当温度为25 ℃、30 ℃、35 ℃、40 ℃时,饱和吸附量分别为250.0 mg/g、322.6 mg/g、400 mg/g、416.7 mg/g.温度升高,吸附量增大,表明该吸附反应是吸热反应.根据热力学函数关系计算出ΔH=35.13 kJ/mol,ΔS=125.17 J/(mol·K),ΔG为-2.13~-4.03 kJ/mol,表明菌体对活性艳红的吸附是自发过程. 相似文献
155.
156.
红壤对铬(VI)吸附特性的研究 总被引:1,自引:0,他引:1
通过云南三类红壤对Cr(VI)吸附行为的研究。结果表明,红壤对Cr(VI)有明显的吸附作用,等温吸附曲线可以用Freundlich方程、Langmuir方程和Temkin方程描述。最大吸附量为红壤>赤红壤>砖红壤。酸度、温度和有机质对红壤吸附Cr(VI)均有影响。低pH值时吸附量随pH值升高略有增加,pH值超过某一限度,吸附量急剧下降,直至基本不吸附;温度低于40℃时,吸附量随温度升高而减少,但温度高于40℃时,吸附量不再减少;随有机质加入量的增加,吸附量减少,其相关性红壤和赤红壤达显著水准,砖红壤达极显著水准。 相似文献
157.
Marcelo H. Cassini 《Conservation biology》2023,37(2):e14037
The International Union for the Conservation of Nature (IUCN) proposes the use of the Environmental Impact Classification for Alien Taxa to standardize the classification of introduced species (IS) based on their environmental impact. The IUCN invoked the precautionary principle (PP) via 2 rules: the impact assigned to a taxon must be the maximum recorded impact across different impact assessments, and when the main driver of environmental damage is unclear, it must be assumed to be caused by the IS. The validity of PP is conditioned on the degree of emergency that warrants urgent decisions and on the scientific evidence demonstrating the advantages of applying a preventive measure. The application of an impact classification system does not arise in the context of an emergency that requires management; it occurs before the decision-making phase. Thus, PP should not be used in early steps of the risk analysis process. The IUCN also did not provide enough scientific basis to justify the use of PP. Instead, the PP rules appear to be rooted primarily in the ethical value system underlying conservation science. Conservationists assign intrinsic value to native species by virtue of their roles and relationships within ecological and evolutionary systems and processes; thus, individuals introduced in new environments not only cease to have value because they are no longer part of that natural diversity and lack those links with the rest of the ecosystem, but they become a threat to what conservationists value most. The consequence of this belief is that all introduced taxa will have an impact at some level, suggesting that values justify the PP rules. 相似文献
158.
Nathalie Cavada Simone Tenan Claudia Barelli Francesco Rovero 《Conservation biology》2019,33(4):873-882
Accurate estimations of the abundance of threatened animal populations are required for assessment of species’ status and vulnerability and conservation planning. However, density estimation is usually difficult and resource demanding, so researchers often collect data at local scales. However, anthropogenic pressures most often have landscape-level effects, for example, through habitat loss and fragmentation. We applied hierarchical distance sampling (HDS) to transect count data to determine the effect of habitat and anthropogenic factors on the density of 3 arboreal primate species inhabiting 5 distinct tropical forests across a landscape of 19,000 km2 in the Udzungwa Mountains of Tanzania. We developed a novel, multiregion extension of HDS that allowed us to model density and detectability jointly across forests without losing site-specific information. For all species, the effect of anthropogenic disturbance on density was overwhelmingly negative among metapopulations: −0.63 Angolan colobus (Colobus angolensis palliatus) (95% Bayesian CI −1.03 to −0.27), −0.54 Udzungwa red colobus (Procolobus gordonorum) (−0.89 to −0.22), and −0.33 Sykes' monkey (Cercopithecus mitis monoides) (−0.63 to −0.07). Some responses to habitat factors were shared, notably the negative effect of elevation and the positive effect of climber coverage. These results are important for conservation science and practice because: the among-populations negative responses to anthropogenic disturbance provides a foundation for development of conservation plans that hold at the landscape scale, which is a comprehensive and cost-efficient approach; the among-species consistency in responses suggests conservation measures may be generalized at the guild level, which is especially relevant given the functional importance of primates in tropical rainforests; and the greater primate densities in areas at low elevation, which are closer to human settlements, point to specific management recommendations, such as the creation of buffer zones and prioritization of areas for protection. 相似文献
159.
Extinction in a hyperdiverse endemic Hawaiian land snail family and implications for the underestimation of invertebrate extinction
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Claire Régnier Philippe Bouchet Kenneth A. Hayes Norine W. Yeung Carl C. Christensen Daniel J. D. Chung Benoît Fontaine Robert H. Cowie 《Conservation biology》2015,29(6):1715-1723
The International Union for Conservation of Nature (IUCN) Red List includes 832 species listed as extinct since 1600, a minuscule fraction of total biodiversity. This extinction rate is of the same order of magnitude as the background rate and has been used to downplay the biodiversity crisis. Invertebrates comprise 99% of biodiversity, yet the status of a negligible number has been assessed. We assessed extinction in the Hawaiian land snail family Amastridae (325 species, IUCN lists 33 as extinct). We did not use the stringent IUCN criteria, by which most invertebrates would be considered data deficient, but a more realistic approach comparing historical collections with modern surveys and expert knowledge. Of the 325 Amastridae species, 43 were originally described as fossil or subfossil and were assumed to be extinct. Of the remaining 282, we evaluated 88 as extinct and 15 as extant and determined that 179 species had insufficient evidence of extinction (though most are probably extinct). Results of statistical assessment of extinction probabilities were consistent with our expert evaluations of levels of extinction. Modeling various extinction scenarios yielded extinction rates of 0.4‐14.0% of the amastrid fauna per decade. The true rate of amastrid extinction has not been constant; generally, it has increased over time. We estimated a realistic average extinction rate as approximately 5%/decade since the first half of the nineteenth century. In general, oceanic island biotas are especially susceptible to extinction and global rate generalizations do not reflect this. Our approach could be used for other invertebrates, especially those with restricted ranges (e.g., islands), and such an approach may be the only way to evaluate invertebrates rapidly enough to keep up with ongoing extinction. 相似文献
160.
通过浓度梯度驯化,从厌氧污泥中分离到一株酸性大红3R脱色菌M3,根据其形态学特征及16S rRNA基因序列分析,鉴定该厌氧菌株为阴沟肠杆菌(Enterobacter cloacae).同时,研究了该菌株在厌氧静置条件下对酸性大红3R的最适脱色条件.结果表明,菌株脱色的最佳营养源为酵母粉,最适宜脱色条件为酵母粉浓度1%、pH =6.5、温度35 ℃、盐度小于4%,在此条件下,对浓度为100 mg·L-1酸性大红3R溶液厌氧静置培养72 h,脱色率达到98%以上.菌株耐盐性良好,在6% ~8%的盐度下具有较好的脱色效果.分光光谱表明,菌株脱色机制主要为生物降解脱色.毒性试验表明,脱色后的酸性大红3R毒性明显降低. 相似文献